Xylella fastidiosa (Xf) is a Gram-negative, xylem-limited bacterium that is transmitted from plant to plant by several xylem-feeding insect vectors. (Hopkins, 1989) Strains of Xylella fastidiosa cause diseases in many economically important plants including grapevines (Pierce's Disease), citrus (Citrus Variegated Chlorosis), peach, plum, oleander, elm, sycamore, oak, maple, and coffee (De Lima et al., 1998; Purcell, 1997). The major symptoms of most Xylella fastidiosa diseases are associated with water-stress, due to reduced xylem flow, which is thought to result from occlusion of the xylem vessels by bacterial aggregates that likely contain EPS (da Silva et al., 2001), gums and tyloses (Hopkins 1989). The onset of disease is as follows: leaf margins progressively dry inward, scorched leaf blades abscise and fall, leaving the petiole attached to the cane (match stick symptom). The canes then lignify irregularly, which produces patches of green tissues surrounded by mature, brown tissue (green island symptom). Finally the whole plant dies. Thus there is a tremendous need to develop plants that are resistant to Xylella fastidiosa infection.